1. Field of the Invention
This invention relates to a cover winding apparatus for opening and closing an opening part of a container by winding to a prescribed position and rewinding to the home position a cover member attached to the opening of the container such as, for example, a magazine cover attached to the opening part of a magazine used in an image forming system. It particularly relates to a cover winding apparatus so configured that the cover member will not form a wrinkle when it is rewound.
2. Description of the Prior Art
In a laser printer, for example, a magazine is used as a container for a recording medium. This magazine contains a photosensitive sheet film as the recording medium. Since the photosensitive agent applied to the film must be kept from exposure to light until the magazine is set in place in the laser printer, a magazine cover for closing the opening part of the magazine is attached to this opening part to shield the interior of the magazine from the ambient light. The magazine cover is detachably attached to the edge of the opening part as with a double-faced adhesive tape. The opening part is opened when the magazine cover is peeled. The opening part is closed to shield the film from the ambient light when the magazine cover is attached again.
U.S. patent application Ser. No. 07/634,702, filed Dec. 27, 1990, now U.S. Pat. No. 5,149,078, disclosed a cover winding apparatus which is configured so as to open and close the opening part of a magazine by winding the magazine cover to a prescribed position and rewinding it to the home position. This cover winding apparatus is provided with a winding roller which is adapted to produce a sliding motion along the upper surface of the magazine and generate a rotation of itself in consequence of the sliding motion so that the magazine cover is wound round the winding roller to open the opening part then the winding roller is rotated to produce the sliding motion in one direction, whereas the magazine cover is rewound from the winding roller to close the opening part when the winding roller is rotated to produce the sliding motion in the opposite direction.
In the conventional cover winding apparatus of this class, after the action of winding the magazine cover and the action of reminding it are repeated a plurality of times, the possibility arises that the magazine cover will draw a wrinkle "floating" at the stop position at which the winding roller completes the action of winding, namely the stop position at which the magazine cover is wound to the prescribed position to open the opening part completely.
This inconvenience is depicted in FIG. 10. FIG. 10 (A) illustrates the state of a winding roller 43 which has assumed the stop position in consequence of completion of the action of winding a magazine cover 32. While the winding roller 43 is in the process of winding the magazine cover 32, the possibility of the cover 32 forming a wrinkle is precluded by carrying out the action of this winding while continuing exertion of tension as indicated by a broken line upon the magazine cover 32. As a result, the exertion of the tension upon the magazine cover 32 persists even after the action of winding has been perfected. Further, in the conventional cover winding apparatus, the stop position at which the winding roller 43 assumes after completion of the action of winding is fixed, depending on the particular kind of magazine.
The tension exerted upon the cover 32 suddenly decreases when the action of rewinding the magazine cover 32 is started as illustrated in FIG. 10 (B) from the state mentioned above. When the action of winding the magazine cover 32 and the action of rewinding it are repeated, the possibility of the cover 32 drawing a wrinkle L near the stop position S assumed by the winding roller 43 on completing the winding action because the tension suddenly decreases at the start of the action of rewinding and further because the stop position S at which the winding roller 43 completes the winding action is fixed. The ease with which the wrinkle L occurs increases when the magazine cover 32 is made of a material susceptible of elongation. The occurrence of the wrinkle L of this nature in the magazine cover 32 entails the disadvantage that the ability of the magazine to shield the film contained therein from the ambient light is affected adversely by this wrinkle L.